The present invention relates to an image display device which utilizes emission of electrons into vacuum, and more particularly to dark current detection means which detects a dark current which flows at the time of occurrence of an abnormal discharge which takes place between an anode electrode and other electrode (control electrode, cathode or the like).
As an image display device which exhibits high brightness and high definition, conventionally, a color cathode ray tube has been popularly used. However, along with the recent demand for achieving high image quality in information processing equipment and television broadcasting, a further demand for a planar display (panel display) which is lightweight and space-saving while having favorable characteristics such as high brightness and high definition is increasing.
As a representative example, a liquid crystal display device, a plasma display device and the like have been commercially available. Further, with respect to the image display device which aims at high brightness particularly, various types of panel-type display devices such as a display device which makes use of emission of electron in vacuum from electron sources (hereinafter referred to as an electron emission type display device or an electric field emission type display device, hereinafter abbreviated as FED) and an organic EL display device which features low power consumption.
FIG. 6 is an enlarged cross-sectional view of the vicinity of one pixel for schematically explaining the basic structure of the FED. In FIG. 6, the FED includes a back substrate SUB1 which forms cathode lines CL which include cathodes K as electric field-emission-type electron sources and a control electrode G1 on an inner surface thereof and a front substrate SUB2 which forms an anode ADE, phosphors PHS and a black matrix BM respectively on an inner surface thereof which faces the back substrate SUB1 in an opposed manner, wherein the FED is constituted by laminating both substrates SUB1, SUB2 by inserting a sealing frame between inner peripheries of both substrates SUB1, SUB2 and by creating a vacuum in the inside of the laminated structure.
Further, there has been also known the structure which provides insulating space holding members ISP between the back substrate SUB1 and the front substrate SUB2 to hold a distance of given size between the back substrate SUB1 and the front substrate SUB2. Here, with respect to these types of prior art, for example, the following patent document 1 and patent document 2 can be exemplified.
[Patent Document 1]
JP-A-10-134701
[Patent Document 2]
JP-A-2000-306508
In the FED having such a constitution, the control electrode G1 which has electron passing holes EHL is provided between the cathodes K which are formed on the cathode line CL on the back substrate SUB1 and the anode ADE which is formed on the front substrate SUB2, wherein by imparting the given potential difference to the control electrode G1 with respect to the cathode line CL, electrons E are pulled out from the cathodes K and the electrons E are made to pass through the electron passing holes EHL of the control electrode G1 and are made to impinge on the phosphors PHS at the anode ADE side, there by performing an image display.